Rock drill

Abstract

A rock drill for percussion drilling comprising a central button insert and a row of outer button inserts. The central button insert extends beyond the outer inserts. For purposes of increasing the drilling rate and the life of the rock drill the ratios of respectively this extent (X) to the diameter (D) of the hole; X:D, and the transverse distance (Y) between the central insert and one of the outer inserts and the diameter (D); Y:D, shall be within predetermined limits.

What I claim is: 
     
       1. A rock drill for percussion drilling comprising a bit body, said bit body including a front face extending generally transversely relative to the longitudinal axis of said bit body, a substantially central button insert of hard material, said central button insert extending longitudinally outwardly of said front face substantially in alignment with said longitudinal axis, and at least a first row of circumferentially spaced outer button inserts of hard material, there being more than two outer inserts disposed on more than two different radii from said axis, said outer button inserts extending outwardly of said front face and being inclined at an angle relative to said longitudinal axis and being arranged to define an outer diameter (D) of the hole drilled by the rock drill, said central and outer inserts each including a working surface disposed on the front of a mounting portion of the insert, said mounting portion being embedded along substantially all of its length within said bit body, said working surface being characterized by an absence of an edge extending radially of said longitudinal axis when viewed along said axis, the improvement wherein the ratio of Y to D is in the range of 8% to 22%, where Y is the distance between opposed side faces on said central button insert and at least one of said outer button inserts when measured at said front face, and the ratio of X to D is no greater than 20%, where X is the outward extent of the outer end of said central button insert beyond a transverse plane through the outer end of at least one of said outer button inserts. 
     
     
       2. A rock drill according to claim 1, wherein the ratio of Y to D is in the range of 10% to 17%. 
     
     
       3. A rock drill according to claim 2, wherein the ratio of Y to D is in the range of 10% to 13% for D up to about 30 mm and 12% to 17% for D above about 30 mm. 
     
     
       4. A rock drill according to claim 1, wherein the ratio of X to D is no greater than 12%. 
     
     
       5. A rock drill according to claim 4, wherein the ratio of X to D is in the range of 5% to 10%. 
     
     
       6. A rock drill according to claim 1, wherein the ratio of X to D is no less than 5%. 
     
     
       7. A rock drill for percussion drilling comprising a bit body, said bit body including a front face extending generally transversely relative to the longitudinal axis of said bit body, a substantially central button insert of hard material, there being more than two outer inserts disposed on more than two different radii from said axis, said central button insert extending longitudinally outwardly of said front face substantially in alignment with said longitudinal axis, and a row of circumferentially spaced outer button inserts of hard material, said outer button inserts extending outwardly of said front face and being inclined at an angle relative to said longitudinal axis and being arranged to define an outer diameter (D) of the hole drilled by the rock drill less than 45 mm, said central and outer inserts each including a working surface disposed on the front of a mounting portion of the insert, said mounting portion being embedded along substantially all of its length within said bit body, said working surface being characterized by an absence of an edge extending radially of said longitudinal axis when viewed along said axis, the improvement wherein the outer end of said central button insert extends beyond a transverse plane through the outer ends of said outer button inserts a distance X ranging up to 8.0 mm and the distance Y between opposed side faces on said central button insert and each of said outer button inserts is in the range of 3.0 mm to 10.0 mm. 
     
     
       8. A rock drill according to claim 7, wherein the distance X is no greater than 4.0 mm and the distance Y is in the range of 3.5 mm to 7.0 mm. 
     
     
       9. A rock drill according to claim 8, wherein the ranges of the distances X and Y are respectively 2.4 mm to 3.0 mm and 4.5 mm to 5.5 mm. 
     
     
       10. A rock drill for precussion drilling comprising a bit body, said bit body including a front face extending generally transversely relative to the longitudinal axis of said bit body, a substantially central button insert of hard material, said central button insert extending longitudinally outwardly of said front face substantially in alignment with said longitudinal axis, and at least a first row of circumferentially spaced outer button inserts of hard material, said outer button inserts extending outwardly of said front face and being inclined at an angle relative to said longitudinal axis and being arranged to define on outer diameter (D) of the hole drilled by the rock drill, the improvement wherein the ratio of Y to D is in the range of 10% to 17%, where Y is the distance between opposed side faces on said central button insert and at least one of said outer button inserts when measured at said front face, the ratio of Y to D being in the range of 10% to 13% for D up to about 30 mm and 12% to 17% for D above about 30 mm. 
     
     
       11. A rock drill for precussion drilling comprising a bit body, said bit body including a front face extending generally transversely relative to the longitudinal axis of said bit body, a substantially central button insert of hard material, said central button insert extending longitudinally outwardly of said front face substantially in alignment with said longitudinal axis, and at least a first row of circumferentially spaced outer button inserts of hard material, said outer button inserts extending outwardly of said front face and being inclined at an angle relative to said longitudinal axis and being arranged to define an outer diameter (D) of the hole drilled by the rock drill, the improvement wherein the ratio of X to D is in the range of 5% to 10%, where X is the outward extent of the outer end of said central button insert beyond a transverse plane through the outer end of at least one of said outer button inserts.